SOLUTION: In how many ways can 11 students be seated in their chairs so that exactly one seats on his or her own chair

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Question 1071464: In how many ways can 11 students be seated in their chairs so that exactly one seats on his or her own chair
Answer by ikleyn(52784) About Me  (Show Source):
You can put this solution on YOUR website!
.
See this Wikipedia article 

     In combinatorial mathematics, a derangement is a permutation of the elements of a set, such that no element appears in its original position. 
     In other words, derangement is a permutation that has no fixed points.



You have here derangements for 10 objects (one of 11 objects is fixed).



Starting with n = 1, the numbers of derangements of n are:

n= 1  2  3  4   5    6     7      8       9       10        11         12

   0, 1, 2, 9, 44, 265, 1854, 14833, 133496, 1334961, 14684570, 176214841, . . .


Your number is   1334961.


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